The International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network will be led by Brooks Jackson, MD, MBA, of Johns Hopkins U, as PI of the Leadership and Operations Center, with Family Health International as the Operations Center. The IMPAACT Statistical and Data Management Center will be headed by David Shapiro, PhD, Harvard U School of Public Health, with Frontier Science & Technology Research Foundation as the Data Management Center. Grace Aldrovandi, MD, U of Southern California will head the IMPAACT Laboratory Center. IMPAACT's mission is to decrease incident HIV and HIV-associated infections including mother-to-child transmission (MTCT) and to decrease mortality/morbidity due to HIV and HIV-associated infections and co-morbidities among infants, children, adolescents, and pregnant/postpartum women worldwide. The above entities will address and support the 5 RFA research priority areas by conducting clinical trials to achieve the following 7 Specific Aims: 1. Evaluate PK, safety, drug interactions of new and existing ARV agents and formulations leading to optimal dosing and licensing for HIV-infected infants, children, adolescents and pregnant women. 2. Evaluate novel approaches for TB prevention, treatment, and diagnosis in HIV-infected children, adolescents, and pregnant women. 3. Develop and test biomedical/behavioral intentions to prevent HIV maternal acquisition and MTCT and to prevent secondary transmission from perinatally HIV-infected adolescents to sexual partners. 4. Evaluate the immunogenicity, safety, and efficacy of vaccines of high priority in HIV-infected pregnant women and their infants, children, and adolescents. 5. Evaluate the potential for HIV cure through therapeutic interventions aimed at prevention and clearance of HIV reservoirs in HIV-infected infants, children and adolescents. 6. Evaluate the PK, safety, and efficacy of new drugs and drug combinations to treat HBV and HCV in HIV infected children, adolescents, and pregnant women. 7. Determine optimal and feasible methods for the prevention and management of co-infections and comorbidities of HIV infection and its treatment.